Abstract The candidate for this K01 application is an Assistant Professor with a well-established, productive program of basic social science research investigating the effects of family relationships, particularly marital conflict, on adolescent health. Her long-term goal is to build upon this research program to develop and test mind-body interventions to improve stress and anxiety in adolescents from high-conflict homes. To do so, the applicant needs additional training in: a) conducting randomized controlled trials (RCTs) of mindfulness interventions and b) assessing the effects of RCTs over time by developing skills in the analysis of intensive longitudinal data. The proposed training plan was developed to provide additional training in these key areas through workshops, didactic courses, in-person mentoring, and primary research activities. The overall goal of the research project is to support the development and testing of an intervention model to directly target a high-risk and underserved adolescent group: those who are from high-conflict homes and are therefore likely to display problems with dysregulated stress physiology, increased stress, and increased anxiety. Past efforts to reduce negative effects of conflict on offspring have focused on targeting family conflict rather than directly focusing on improving regulation in adolescents who are at-risk. Mindfulness interventions represent a promising approach to directly target adolescents from high-conflict homes to build regulatory capabilities. However, they have not been used in this way, nor have ecological momentary intervention (EMI) supplements to these interventions been developed. Incorporating EMI into traditional treatments often increases treatment efficacy, and is particularly appropriate for adolescents. The specific aims are to: 1) develop an EMI supplement (intervention content delivered via cell phone between sessions) to Learning to Breathe (L2B), an evidence-based mindfulness program for adolescents, and to determine the best delivery plan for this EMI supplement via a mixed methods study; 2) evaluate the feasibility and acceptability of L2B Plus (L2B plus EMI) for adolescents from high-conflict homes, and, 3) examine the extent to which mindfulness reduces physiological stress dysregulation, perceived stress, and anxiety in adolescents from high-conflict homes, both a) experimentally by comparing L2B to a control, health education program and b) observationally in an existing dataset. In both studies, links between mindfulness, stress, and anxiety will be examined between- and within-person. In line with NCCIH?s focus on investigating how mind-body practices improve stress and anxiety, the current project will advance understanding of how increasing mindfulness can support adolescents from high-conflict homes; this project is expected to result in a flexible intervention model that is feasible to implement and well-liked by families and adolescents, and that can be modified to broadly serve adolescents at-risk because of chronic stress. This study is also expected to result in the key pilot data supporting a larger-scale RCT of L2B Plus.